Packages

package atomic

A small toolkit of classes that support compare-and-swap semantics for safe mutation of variables.

On top of the JVM, this means dealing with lock-free thread-safe programming. Also works on top of Javascript, with Scala.js, for API compatibility purposes and because it's a useful way to box a value.

The backbone of Atomic references is this method:

def compareAndSet(expect: T, update: T): Boolean

This method atomically sets a variable to the update value if it currently holds the expect value, reporting true on success or false on failure. The classes in this package also contain methods to get and unconditionally set values.

Building a reference is easy with the provided constructor, which will automatically return the most specific type needed (in the following sample, that's an AtomicDouble, inheriting from AtomicNumber[T]):

val atomicNumber = Atomic(12.2)

atomicNumber.incrementAndGet()
// => 13.2

These also provide useful helpers for atomically mutating of values (i.e. transform, transformAndGet, getAndTransform, etc...) or of numbers of any kind (incrementAndGet, getAndAdd, etc...).

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Type Members

  1. abstract class Atomic [A] extends Serializable

    Base trait of all atomic references, no matter the type.

  2. final class AtomicAny [T <: AnyRef] extends Atomic[T]

    Atomic references wrapping AnyRef values.

    Atomic references wrapping AnyRef values.

    T

    is forced to be an AnyRef because the equality test is by reference and not by value.

  3. final class AtomicBoolean extends Atomic[Boolean]

    Atomic references wrapping Boolean values.

    Atomic references wrapping Boolean values.

    Note that the equality test in compareAndSet is value based, since Boolean is a primitive.

  4. trait AtomicBuilder [A, R <: Atomic[A]] extends Serializable

    For a given A indicates the most specific Atomic[A] reference type to use.

    For a given A indicates the most specific Atomic[A] reference type to use.

    In essence this is implementing a form of specialization driven by implicits.

  5. final class AtomicByte extends AtomicNumber[Byte]

    Atomic references wrapping Byte values.

    Atomic references wrapping Byte values.

    Note that the equality test in compareAndSet is value based, since Byte is a primitive.

  6. final class AtomicChar extends AtomicNumber[Char]

    Atomic references wrapping Char values.

    Atomic references wrapping Char values.

    Note that the equality test in compareAndSet is value based, since Char is a primitive.

  7. final class AtomicDouble extends AtomicNumber[Double]

    Atomic references wrapping Double values.

    Atomic references wrapping Double values.

    Note that the equality test in compareAndSet is value based, since Double is a primitive.

  8. final class AtomicFloat extends AtomicNumber[Float]

    Atomic references wrapping Float values.

    Atomic references wrapping Float values.

    Note that the equality test in compareAndSet is value based, since Float is a primitive.

  9. final class AtomicInt extends AtomicNumber[Int]

    Atomic references wrapping Int values.

    Atomic references wrapping Int values.

    Note that the equality test in compareAndSet is value based, since Int is a primitive.

  10. final class AtomicLong extends AtomicNumber[Long]

    Atomic references wrapping Long values.

    Atomic references wrapping Long values.

    Note that the equality test in compareAndSet is value based, since Long is a primitive.

  11. abstract class AtomicNumber [T] extends Atomic[T]

    Represents an Atomic reference holding a number, providing helpers for easily incrementing and decrementing it.

    Represents an Atomic reference holding a number, providing helpers for easily incrementing and decrementing it.

    T

    should be something that's Numeric

  12. final class AtomicNumberAny [T <: AnyRef] extends AtomicNumber[T]

    Atomic references wrapping any values implementing Scala's Numeric type-class.

    Atomic references wrapping any values implementing Scala's Numeric type-class.

    Note that the equality test in compareAndSet is reference based. This is because we are storing AnyRef references and on top of the JVM that's the semantic of compareAndSet. This behavior is kept consistent even on top of Scala.js / Javascript.

  13. final class AtomicShort extends AtomicNumber[Short]

    Atomic references wrapping Short values.

    Atomic references wrapping Short values.

    Note that the equality test in compareAndSet is value based, since Short is a primitive.

  14. sealed abstract class PaddingStrategy extends AnyRef

    For applying padding to atomic references, in order to reduce cache contention.

    For applying padding to atomic references, in order to reduce cache contention. JEP 142 should reduce the need for this along with the @Contended annotation, however that might have security restrictions, the runtime might not act on it since it's just a recommendation, plus it's nice to provide backwards compatibility.

    See: http://mail.openjdk.java.net/pipermail/hotspot-dev/2012-November/007309.html

    The default strategy is NoPadding. In order to apply padding:

    import monix.execution.atomic.Atomic
    import monix.execution.atomic.PaddingStrategy.Right64
    
    val paddedAtomic = Atomic.withPadding(10, Right64)
    See also

    PaddingStrategy.LeftRight256

    PaddingStrategy.Right128

    PaddingStrategy.Left128

    PaddingStrategy.LeftRight128

    PaddingStrategy.Right64

    PaddingStrategy.Left64

    PaddingStrategy.NoPadding

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